Method and apparatus for generating gaseous mixtures for inflatable devices

ABSTRACT

A pyrotechnically operated inflating apparatus is disclosed for generating gaseous inflation mixtures of carbon dioxide and combustion products of propellants. The apparatus includes a container for storing primary fluid inflation media. A control head is mounted on the container to govern the discharge of the primary fluid into an inflatable. The control head is provided with an internal space containing a pyrotechnic charge to generate, upon ignition, high temperature gases as secondary inflation media. A quantity of the secondary media is initially diffused throughout the container to elevate the pressure of the primary media to effect discharge from the container. The remainder of the secondary media is mixed with the discharging primary media at a downstream outlet orifice within the control head immediately prior to entry into the inflatable.

United States Patent [1 1 Munn METHOD AND APPARATUS FOR GENERATINGGASEOUS MIXTURES FOR INFLATABLE DEVICES Alfred John Munn, Wayne, NJ.

Walter Kidde & Company, Inc., Belleville, NJ.

Filed: Apr. 21, 1972 Appl. No.: 246,365

Inventor:

Assignee:

US. Cl 141/4, 9/11 A, 9/321, 23/281, 62/48, 222/3 Int. Cl B65b 3/04Field of Search 141/4; 9/11 A, 316, 319, 9/321, 325, 311; 222/3; 62/48;23/281; 280/150 AB; 102/39 References Cited UNITED STATES PATENTS Wismar9/321 X 3,689,105 9/1972 Matsuietal. ..222/3x Primary Examiner-HoustonS. Bell, Jr. Attorney, Agent, or FirmDarby & Darby [5 7] ABSTRACT Apyrotechnically operated inflating apparatus is disclosed for generatinggaseous inflation mixtures of carbon dioxide and combustion products ofpropellants. The apparatus includes a container for storing primaryfluid inflation media. A control head is mounted on the container togovern the discharge of the primary fluid into an inflatable. Thecontrol head is provided with an internal space containing a pyrotechniccharge to generate, upon ignition, high temperature gases as secondaryinflation media. A quantity of the secondary media is initiallydifi'used throughout the container to elevate the pressure of theprimary media to effect discharge from the container. The remainder ofthesecondary media is mixed with the discharging primary media at adownstream outlet orifice within the control head immediately prior toentry into the inflatable.

13 Claims, 5 Drawing Figures FIG.

PATENTEU 1 74 M1 I III This invention relates to apparatus for chargingor pressurizing an inflatable device such as a life raft, and

BACKGROUND OF THE INVENTION For many years, inflatable devices have beenemployed as flotation equipment, such as life rafts and the like. It hasbeen customary to use liquefied carbon dioxide as a source of pressuremedia for inflating such devices. Carbon dioxide is particularlysuitable because of its high storage density, relatively low storagepressure, non-flammability, low toxicity and its ability to bedischarged at extremely low temperatures, for example, minus 65Fahrenheit.

One difficulty with carbon dioxide is its tendency, upon expansion intoan inflatable bag or envelope, to produce carbon dioxide snow or coldcarbon dioxide gas, with the result that full inflation cannot beobtained within the short period of time required for emergencyactivation. Furthermore, carbon dioxide at low temperatures has beenfound to causesome damage to'the material constituting the inflatable.

For this reason, it has been customary, heretofore, to mix the liquefiedcarbon dioxide with hot gaseous combustion products of propellants, suchas burning powders, prior to escape of the carbon dioxide from thecontainer in which it is stored under pressure. The hot combustionproducts heat the liquefied carbon dioxide to effect a change of stateto the gas form, thereby to raise the pressure of the carbon dioxide toa predetermined level prior to release into the inflatable. In somecases, the carbon dioxide is retained in its storage container by afrangible disc until the pressure within the container rises to apredetermined level suitable for full inflation of the air bag. The discruptures upon attainment of the required pressure, and the carbondioxide gas evacuates its container to fill the inflatable.

One difficulty with this prior type of inflation system is the inabilityadequately to control the build-up of thermal energy within the storagecontainer upon ignition of the solid or liquid propellants. It has beenfound, for example, that these solid and liquid propellants release anexcess of thermal energy to raise the tempera ture of the carbon dioxidebeyond an acceptable level. This inability to restrain the build-up ofthermal energy within the storage container has heretofore given rise toseveral important difficulties. One difficulty has been that aninflatable charged to the proper level with hot or warm carbon dioxidewill become inadequately inflated upon subsequent cooling of thepressurizing gases. A prior solution to this problem has been to deliverthe inflating gas at an excessively high pressure. This. in turn, hasgiven rise to the possibility that damage to the inflatable fabric mayoccur as a result of such high initial pressures.

, Accordingly, the primary object of the present invention is to providea pyroteehnically operated inflating apparatus which effects acontrolled mixing of the hot and cold properties of the pyrotechnic andcarbon dioxide gases, so that the inflatable may be charged initially toan adequate and constant pressure with the inflation media at atemperature the fabric.

In the preferred embodiment, this object is accomwhich willnot damageplished by providing inflating apparatus which consists of a containerof fluid medium under pressure having an opening at one end, and acontrol head closing the opening and having an internalspace whichcontains a pyrotechnic charge to generate high temperature gases uponignition. Means are provided for diffusing throughout the fluid medium aquantity of the high temperature gases generated by the pyrotechniccharge. This raises the temperature and pressure of the fluid medium bya predetermined amount and causes the fluid medium to discharge throughan outlet passage formed in the control head externally of thecontainer. The remainder of the high temperature gases produced by thepyrotechnic charge is directed to the outlet passage to be mixed withthe carbon dioxide fluid downstream from the storage container at anoutlet orifice opening to the inflatable.

According to the invention, therefore, the tempera substantial portionof the pyrotechnic gases is mixed with the fluid medium at thedownstream outlet orifice, its thermal energy is partially dissipated bythe Joule- Thompson effect from expansion through the orifice into theinflatable. The temperature of the pressure media in the inflatable istherefore lower than that which has been attainable in the priorsystems, in which all of the thermal energy of the pyrotechnic gases isutilizedto heat the stored fluid medium prior to discharge.

The chances of damage to the fabric as a result of unduly high thermalenergy in the inflating fluid are therefore minimized. An additionaladvantage of the present invention is that a smaller initial volume ofcarbon dioxide may be stored in the storage container, thereby reducingthe weight of the system.

One object of the present invention, therefore, is to providepyrotechnically-operated inflating apparatus which is capable ofproviding a full inflation response at temperatures low enough to avoiddamage to the fabric of the inflatable.

Another object is to provide pyrotechnicallyoperated inflating apparatuswhich effects a full inflation response at pressures which remainsubstantially constant after the initial charging of the inflatable.

Still another objectis to provide pyrotechnicallyoperated inflatingapparatus which is capable of effecting a full inflation response inunder ten seconds.

Yet another object is to provide inflating apparatus having a wideoperating temperature range from approximately minus 65 Fahrenheit toplus Fahren heit.

A further object is to provide a closed inflation device which isoperable in any attitude independent of Yet another object is to providea closed inflation device which employs the use of non-toxic gaseshaving no harmful effects to the inflatable material.

A still further object is to provide a closed inflation device which issimple, reliable, and inexpensive to manufacture.

DESCRIPTION OF THE DRAWINGS For a further understanding of the presentinvention, reference may be had to the accompanying drawings, in whichfFIG. 1 is an elevated top view, partially cut away, of a closedinflation device in accordance with the present invention;

FIG. 2 is a top sectional view of the control head portion of theapparatus of FIG. 1;

FIG. 3 is a view taken along the line 33 of FIG. 1;

FIG. 4 is a view taken along the line 44 of FIG. 2; and

FIG. 5 is a cross-section along lines 5-5 of FIG. 2.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to thedrawings, and in particular to FIG. 1, inflating apparatus isillustrated which generally consists of a container for storing a fluidmedium such liquid carbon dioxide or the like under pressure, and acontrol head, generally indicated by reference numeral 11, which isconnected to one end of the container for governing the operation of theapparatus. The entire apparatus as shown in FIG. 1 is to be used inconnection with an inflatable device (not shown) which may be a bag ofany desired shape and size. The apparatus is particularly adapted foruse in inflating boats, rafts, rescue devices, helicopter landing padsor the like.

As illustrated in FIG. 1, a portion of the container 10 is broken awayto reveal the interior. In the preferred embodiment illustrated, anelongated diffuser tube 12 extends partway into the containersubstantially along the longitudinal axis of the container. The functionof the diffuser tube will be explained in greater detail below.Illustratively, however, the diffuser tube extends inwardly of thecontainer 10 from the control head 11, and is preferably provided with aplurality of orifices 13 positioned around its circumference and at itsfree end to establish fluid flow communication between the interior ofthe tube and the contents of the container. It has been found that thepresent apparatus operates satisfactorily where the extent ofpenetration of the tube into the interior of the container isapproximately 50%, as illustrated.

The container 10 is preferably provided with an elongated outwardlyextending neck portion 14 which forms an outlet 16. In the preferredembodiment, the outer surface area of the neck 14 is threaded forengagement with a correspondingly threaded receptacle formed as part ofthe control head ll.

The control head is preferably substantially cylindrical in shape, andis provided with a cylindrical lower portion 17 which is intemallythreaded to receive the neck 14 of the container 10. In this way, thecontrol head 11 may be screwed down tightly to its operating position onthe neck 14.

The interior of the control head 11 is shown in cross section in FIG. 2.The control head is provided with a substantially cup-shaped formation18 which is positioned so as to form an internal hot gas generatingchamber, generally indicated by reference numeral 19. A substantiallycylindrical preferably solid propellant charge 21 is situated within thechamber 19. Such a charge may be ignited by a plurality of ignitionpellets 22 which generate initial heat sufficient to ignite the charge.

In the present embodiment, the pellets 22 are ignited by means of apercussion-actuated explosive, such as a cartridge 23. A manuallyoperated trigger mechanism, generally indicated by reference numeral 24,is provided as part of the control head and consists of an impactplunger 26 slidably mounted within an appropriate guide channel 27 forstriking the cartridge to effect ignition of the propellant charge.

It should be understood that an electrically actuated squib or apressure-responsive ignition may also be employed, depending upon theparticular use to which the inflating apparatus is to be put. Themanually actuated ignition is preferred for use with inflation devicesfor life rafts and the like.

The impact plunger 26 is biased inwardly toward the cartridge 23,illustratively by means of a coil spring 28. The plunger is preferablyof two-piece construction, consisting of an inner striker portion 29 andan outer shaft portion 31. Upon a predetermined compression of thespring 28, the striker portion separates from the shaft. Suchcompression of the spring is achieved, for example, by means of apulling lanyard or cable 32 (FIG. 1) which is pulled so as to move theplunger outwardly to compress the spring 28. Upon release, the strikerportion 29 is driven inwardly under impetus from the spring 28 to firethe cartridge 23.

The control head 1 l is further provided with an internal passage 33which extends between the hot gas generating chamber 19 and the outlet16 of the storage container 10. In the present embodiment, the diffusertube 12 is connected to the control head 1 1 so as to be in fluid flowcommunication with the passage 33, whereby a quantity of the hot gasesgenerated within the chamber 19 may be conducted through the passage 33into the diffuser tube to be mixed with the fluid medium stored withinthe container 10. The diffuser tube 12 is preferably threaded to thecontrol head 11, as indicated by reference numeral 34.

In accordance with the present invention, there is provided apressure-rupturable or frangible disc 36 to seal the passage 33 adjacentthe opening to the hot gas chamber 19, effectively to separate the fluidinflation media from the propellant mixture prior to actuation of thedevice. Upon ignition of the charge 21, hot gases are generated whichincrease the pressure within the chamber 19. When this pressure build-upreaches a predetermined value, the disc 36 ruptures to permit the hotgases to flow from the chamber 19 through the passage 33 and into thediffuser tube 12. From there, the gases flow through the variousorifices 13 of the diffuser tube and into the container 10 to mix withthe carbon dioxide.

The outlet assembly of the control head 11 is depicted in FIGS. 4 and 5.In the preferred embodiment, the outlet assembly consistsiessentially ofan outwardly protruding formation 35 having an outlet conduit 37 whichextends from and is in fluid flow communication with the internalpassage 33. A downstream propellant orifice, indicated by referencenumeral 38, is provided at the juncture between the passage 33 and theoutlet conduit. A second pressure-rupturable or frangible disc 39 isprovided outwardly of the downstream propellant orifice 38, to seal theoutlet conduit 37 thereby to prevent discharge through the outlet priorto the attainment of an inflation media pressure sufficient fully tocharge the inflatable device. A non-recoil configuration is preferablyprovided at the outlet end of the discharge conduit 37. A non-recoilmechanism for the present circumstances can take several forms, apreferred form including a pair of diametrically opposite side ports 41and 41a, which serve to direct the discharging fluid in oppositedirections substantially perpendicular to the outlet conduit. In thisway, discharge reaction forces are minimized to prevent recoil of theapparatus upon actuation. Where desired, the non-recoil can also takethe form of a separate cap member (not shown) having a pair ofdiametrically opposedside ports. Such a cap member may be constructed soas to fit over the discharge end of the outlet conduit.

As a precaution against the advent of intolerably high pressures beingcreated within the container should a malfunction occur somewhere in thesystem, an overboard safety relief system 42 is provided in the controlhead 11. A second internal passage 43 may be formed within the controlhead to extend between the outlet 16 of the container 10 and a safetyrelief vent 44. A pressure-rupturable disc 46 is provided to seal thepassage 43 to prevent the inadvertent escape of the fluid inflationmedium. Should the pressure within the container 10 rise to an unsafelevel, the disc 46 will rupture to vent the fluid to the atmospherethrough the passage 43 and the safety outlet 44. In the preferredembodiment, a non-recoil plug 47 is threaded into the control head bothto secure the burst disc 46 in position across the passage 43, and toprovide a pair of side ports, including the vent 44, to minimize theeffect of discharge reaction forces arising upon the evacuation of fluidfrom the container, asdescribed above.

In the prior type of inflation apparatus, a pyrotechnic charge ispositioned within the storage container to facilitate the transfer ofthermal energy to the inflation media. Under such circumstances, heatdissipation through the walls of the pyrotechnic chamber has not causedserious difficulties insofar as it was thought desirable to maximize thetransfer of thermal energy to the carbon dioxide. 1

In the preferred embodiment of the present invention, the pyrotechniccharge and chamber are formed as part of the external control head.Under these circumstances, it is important to minimize heat loss throughthe walls of the pyrotechnic chamber. I

In accordance with the invention, the outer diameter of the pyrotechnicchamber 19 is slightly less than the inner diameter'of the chamber 18,so that a relatively thin substantially annular space 51 is left betweenthe charge and the chamber walls. 'A substantially cylindricalcorrugated shield member 52 may be provided in the space 51. Thecorrugations in the shield 52 are such that the shieldis simultaneouslyin contact with both the outer surface area of the pyrotechnic chargeand the inner surface area of the chamber wall. Priorto ignition of thecharge, the shield 52 serves to stabilize the position of the chargewithin the chamber. By way of example, the corrugated shield 52 may be athin skin nular space 51 as a further heat shield. The outer shield 53is preferably positioned between the corrugated shield 52 and thechamber wall. By way of example, the outer shield 53 may consist of arelatively thin skin-like metal material approximately 0.001 inches inthickness.

One end of the ignition chamber 18 may be coated with a heat resistantresilient filler material 54, such as silicon rubber. In the preferredembodiment, the coating 54 is located at the distal or outer end of thechamber, and has a substantially planar inner face 55 which engages thecorresponding ends of the pyrotechnic charge 19 and the heat shields 52and 53. The rubber filling 54 serves to retain and to protect fromdamage the contents of the assembled pyrotechnic chamber in theeventthat the inflation unit is subjected to external vibrations or shocks.After ignition of the charge, the rubber filling also acts in aninsulative capacity to minimize dissipation of heat generated by theburning charge, through the end wall of the chamber.

Inflation systems of the present type may be initially charged withinflation media by utilizing several known techniques. In the presentembodiment, the fluid medium is injected through the outlet conduit 37.Passages 56 and'56a are provided in the outlet formation or nozzle 35 tocarry the charging fluid into a space 57 surrounding the inner end ofthe nozzle within the control head. During the charging or fillingoperation the nozzle 35 is only partially threaded into engagement withthe control head. Accordingly, there is a continuous passage extendingfrom one portion of the outlet conduit through the space 57 to aninwardly displaced portion of the conduit.

The burst disc 39 is preferably retained as part of the removable nozzleassembly by means of a gasket 58 and retainer ring 59. As the system isfilled, the inflation fluid is diverted around the burst disc by meansof the passages 56 and 56a and the space 57. In the preferredembodiment, the upper portion 62 of the outlet conduit 37 permitscharging of the system by conducting the injected fluid medium through apassage 61 in the control head to the interior of the container 10. Whenfilling is complete, the nozzle assembly is screwed down tight to sealthe passage 57 from the outlet conduit inwardly of the burst disc 39.

In operation, an inflatable device is attached, in its deflatedcondition, to the nozzle assembly 35 of the control head 11. Theinflation of the inflatable device is effected by pulling the cable orlanyard 32 to move the impact plunger 26 outwardly against the bias ofthe spring 28. At the appropriate point, the striker portion 29separates from the shaft 31 and the action of the spring forces itinwardly to impactagainst the percussion-actuated explosive cartridge23. The impact of the striker 29 against'the end of the cartridge causesthe cartridge to detonate and produce a flash which initially ignitesthe igniter pellets 22. The charge 21 then burns to produce hot gaseswhich increase the pressure within the chamber 18 thereby applyingpressure to the rupturable disc 36. When this pressure reaches apredetermined level, the disc 36 bursts and the hot gases flow throughthe passageway 33 and into the container 10 by means of the diffusertube 12. Initial mixing, thereduit 37. it mixes there with hot gassupplied through the downstream-propellant orifice 38 and into the upperoutlet conduit 62, thereby applying pressure to the outlet rupturabledisc 39. The pressure within the container 10 increases rapidly to avalue which causes the disc 39 to rupture. The gaseous carbon dioxideand the pyrotechnic gases then flow through the outlet conduit 37 andthrough the side ports 41 and 41a and from there into the inflatabledevice to effect the inflation thereof.

Since the pressure against the rupturable disc 39 rises very rapidly tothe burst point, the entire supply of pyrotechnic gases generated withinthe chamber 18 of the control head 11 is not exhausted at the time thatthe outlet disc 39 ruptures. In accordance with the inven tion, furthermixing between the pyrotechnic gases and the fluid inflation mediumoccurs at the downstream orifice 38 during discharge into the inflatabledevice.

This downstream mixing of pyrotechnic gases and carbon dioxide is animportant feature of the present invention. As indicated above, onedifficulty with the prior type of inflation system has been theinability of such systems adequately to control the build-up of thermalenergy within the container. in part, this has been due to the fact thatin the prior type of system all of the hot gases generated by thepyrotechnic charge have been evacuated directly into the container. Thusit has frequently occurred that in such systems, the temperature andpressure of the carbon dioxide is raised beyond an acceptable level.

According to the present invention, only that portion of the pyrotechnicgases required to elevate the pressure of the stored carbon dioxide to alevel sufficient to burst the outlet disc 39 is actually mixed with thecarbon dioxide within the container 10. Upon rupture of the outlet disc,the majority of the remaining hot pyrotechnic gases mixes with thedischarging fluid medium at the downstream orifice, giving rise to thepredictable cooling effect of the Joule-Thompson principle upon entryinto the inflatable device.

Furthermore. utilization of the pyrotechnic gases to augment theinflation charge may enable the use of a smaller quantity of carbondioxide and consequently a smaller storage container, to effect areduction in weight for the system.

What is claimed is:

1. Apparatus for inflating an inflatable device, comprising:

means having first and second interconnected zones for containing fluidinflation media under pressure;

a container for holding a charge of primary fluid inflation media underpressure within said first zone;

ing said pyrotechnic charge to generate high temperature secondary fluidinflation media;

means for introducing said secondary fluid media to both said first andsecond zones to form a first fluid mixture in said first zone having oneproportion of secondary to primary fluid media, and a second fluidmixture in said second zone incuding the first fluid mixture having agreater proportion of secondary to primary fluid media, said introducingmeans including a diffuser tube having one end in communication withsaid control assembly for receiving the high temperature secondary fluidinflation media and also in communication with said second zone, theother end of said diffuser tube extending inwardly of said container andhaving a plurality of orifices positioned around its circumference toallow fluid within the tube to pass into said container; and

means for introducing said second fluid mixture to said inflatabledevice.

2. The apparatus of claim 1 wherein the interconnection between saidzones comprises a conduit to conduct the-passage of fluid from one zoneto the other.

3. The apparatus of claim 2 wherein said diffuser tube is in fluid flowcommunication with said conduit, and a first pressure-sensitive elementnormally sealing said conduit and having a pressure surface in fluidflow communication with said second zone, said first element beingadapted to burst when the pressure within said second zone reaches afirst predetermined value to release the second fluid mixture.

4. The apparatus of claim 3 wherein said means for introducing said hightemperature secondary fluid to said second zone includes an orificeformer between said second zone and the pyrotechnic charge, said conduithaving an outlet passage extending from said second zone to providefluid flow communication with the inflatable device.

5. The apparatus of claim 4 further comprising means forming a secondoutlet passage from said first zone, a second pressure-sensitive elementnormally sealing said second outlet passage and having a pressuresurface in fluid flow communication with the primary fluid of said firstzone and, said second element being adapted to burst when the pressurewithin said first .zone reaches a second predetermined value greaterthan said first value, and means communicating with said second outletpassage to enable the primary fluid to vent when said second elementbursts.

6. Apparatus for inflating an inflatable device, comprising:

an enclosure having first and second interconnected but separatelydefined zones for containing fluid inflation media under pressure;

a charge of primary fluid inflation media within said first zone;

a control assembly mounted on said enclosure and having a chambercontaining a pyrotechnic charge;

means forming part of said control assembly for igniting saidpyrotechnic charge to generate high temperature secondary fluidinflation media;

means substantially enveloping said pyrotechnic charge for retainingwithin said chamber thermal energy generated by ignition of said charge;

means for introducing said secondary fluid media to said first andsecond zones to form a first fluid mixture in said first zone having oneproportion of secondary to primary fluid media, and a second fluidmixture in said second zone having a greater proportion of secondary toprimary fluid media; and means for introducing said second fluid mixtureto said inflatable device.

7. The apparatus of claim 6 wherein said enveloping means comprises atleast a first substantially cylindrical heat shield within said chamberand surrounding a major portion of the surface area of said pyrotechniccharge.

8. The apparatus of claim 7 wherein said heat shield is corrugated.

9. The apparatus of claim 8 wherein said enveloping means furthercomprises a second substantially cylin drical heat shield memberpositioned between said corrugated shield and the internal walls of saidchamber.

10. The apparatus of claim 6 wherein said enveloping means comprises aheat-resistant resilient material coating one end of said chamber, andhaving a substantially planar inner surface engaging the correspondingend of said pyrotechnic charge.

11. The apparatus of claim 10 wherein said resilient material comprisessilicone rubber.

12. The method of inflating an inflatable device comprising:

generating a predetermined charge of hot gases under pressure in aconfined volume;

mixing said gases with a predetermined charge of carbon dioxide underpressure in a first confined zone to increase the pressure of the carbondioxide, said mixing being limited to maintain a greater pressure withinsaid confined volume than within said first confined zone; I

releasing the mixture of gases and carbon dioxide from said first zone;

passing said mixture from said first zone to a second confined zone;

mixing said gaseswith said mixture'in said second zone to increase thepressure of said mixture, said mixing being limited to maintain agreater pressure expanding said mixture from said second zone to coolsaid mixture; and

introducing the expanded mixture into the inflatable device.

13. Apparatus for inflating an inflatable device, com- 10 prising:

means for containing a charge of primary fluid inflation media within afirst zone;

means defining a second zone including means for interconnecting saidfirst and second zones,

a control assembly containing a pyrotechnic charge;

said control assembly including means for igniting said pyrotechniccharge to produce a high temperature secondary fluid inflation media;

an outlet conduit communicating with said second zone and including arupturable pressure responsive device therein for normally blockingdischarge of fluid from said outlet conduit, and

means for introducing said secondary fluid media to both said first andsecond zones at all times that said secondary fluid is being produced toform a first fluid mixture in said first zone having one proportion ofsecondary to primary fluid media, the first mixture being conveyed bysaid interconnecting means to form a second fluid mixture in said secondzone having a greater proportion of secondary to primary fluid media,said pressure responsive means being ruptured in response to the fluidpresent in said second zone at a predetermined pressure to permitdischarge of the second fluid mixture from said outlet conduit; and

means for introducing said second fluid mixture to said inflatabledevice.

1. Apparatus for inflating an inflatable device, comprising: means having first and second interconnected zones for containing fluid inflation media under pressure; a container for holding a charge of primary fluid inflation media under pressure within said first zone; a control assembly for housing a pyrotechnic charge; means forming part of said control assembly for igniting said pyrotechnic charge to generate high temperature secondary fluid inflation media; means for introducing said secondary fluid media to both said first and second zones to form a first fluid mixture in said first zone having one proportion of secondary to primary fluid media, and a second fluid mixture in said second zone incuding the first fluid mixture having a greater proportion of secondary to primary fluid media, said introducing means including a diffuser tube having one end in communication with said control assembly for receiving the high temperature secondary fluid inflation media and also in communication with said second zone, the other end of said diffuser tube extending inwardly of said container and having a plurality of orifices positioned around its circumference to allow fluid within the tube to pass into said container; and means for introducing said second fluid mixture to said inflatable device.
 2. The apparatus of claim 1 wherein the interconnection between said zones comprises a conduit to conduct the passage of fluid from one zone to the other.
 3. The apparatus of claim 2 wherein said diffuser tube is in fluid flow communication with said conduit, and a first pressure-sensitive element normally sealing said conduit and having a pressure surface in fluid flow communication with said second zone, said first element being adapted to burst when the pressure within said second zone reaches a first predetermined value to release the second fluid mixture.
 4. The apparatus of claim 3 wherein said means for introducing said high temperature secondary fluid to said second zone includes an orifice former between said second zone and the pyrotechnic charge, said conduit having an outlet passage extending from said second zone to provide fluid flow communication with the inflatable device.
 5. The apparatus of claim 4 further comprising means forming a second outlet passage from said first zone, a second pressure-sensitive element normally sealing said second outlet passage and having a pressure surface in fluid flow communication with the primary fluid of said first zone and, said second element being adapted to burst when the pressure within said first zone reaches a second predetermined value greater than said first value, and means communicating with said second outlet passage to enable the primary fluid to vent when said second element bursts.
 6. Apparatus for inflating an inflatable device, comprising: an enclosure having first and second interconnected but separately defined zones for containing fluid inflation media under pressure; a charge of primary fluid inflation media within said first zone; a control assembly mounted on said enclosure and having a chamber containing a pyrotechnic charge; means forming part of said control assembly for igniting said pyrotechnic charge to generate high temperature secondary fluid inflation media; means substantially enveloping said pyrotechnic charGe for retaining within said chamber thermal energy generated by ignition of said charge; means for introducing said secondary fluid media to said first and second zones to form a first fluid mixture in said first zone having one proportion of secondary to primary fluid media, and a second fluid mixture in said second zone having a greater proportion of secondary to primary fluid media; and means for introducing said second fluid mixture to said inflatable device.
 7. The apparatus of claim 6 wherein said enveloping means comprises at least a first substantially cylindrical heat shield within said chamber and surrounding a major portion of the surface area of said pyrotechnic charge.
 8. The apparatus of claim 7 wherein said heat shield is corrugated.
 9. The apparatus of claim 8 wherein said enveloping means further comprises a second substantially cylindrical heat shield member positioned between said corrugated shield and the internal walls of said chamber.
 10. The apparatus of claim 6 wherein said enveloping means comprises a heat-resistant resilient material coating one end of said chamber, and having a substantially planar inner surface engaging the corresponding end of said pyrotechnic charge.
 11. The apparatus of claim 10 wherein said resilient material comprises silicone rubber.
 12. The method of inflating an inflatable device comprising: generating a predetermined charge of hot gases under pressure in a confined volume; mixing said gases with a predetermined charge of carbon dioxide under pressure in a first confined zone to increase the pressure of the carbon dioxide, said mixing being limited to maintain a greater pressure within said confined volume than within said first confined zone; releasing the mixture of gases and carbon dioxide from said first zone; passing said mixture from said first zone to a second confined zone; mixing said gases with said mixture in said second zone to increase the pressure of said mixture, said mixing being limited to maintain a greater pressure within said confined volume than within said second zone; expanding said mixture from said second zone to cool said mixture; and introducing the expanded mixture into the inflatable device.
 13. Apparatus for inflating an inflatable device, comprising: means for containing a charge of primary fluid inflation media within a first zone; means defining a second zone including means for interconnecting said first and second zones, a control assembly containing a pyrotechnic charge; said control assembly including means for igniting said pyrotechnic charge to produce a high temperature secondary fluid inflation media; an outlet conduit communicating with said second zone and including a rupturable pressure responsive device therein for normally blocking discharge of fluid from said outlet conduit, and means for introducing said secondary fluid media to both said first and second zones at all times that said secondary fluid is being produced to form a first fluid mixture in said first zone having one proportion of secondary to primary fluid media, the first mixture being conveyed by said interconnecting means to form a second fluid mixture in said second zone having a greater proportion of secondary to primary fluid media, said pressure responsive means being ruptured in response to the fluid present in said second zone at a predetermined pressure to permit discharge of the second fluid mixture from said outlet conduit; and means for introducing said second fluid mixture to said inflatable device. 